Local exchange carriers and interconnect common carriers provide a subaccount billing service in which charges for telephone calls of a customer are sorted and listed under separate subaccount numbers assigned by the customer. This is a particularly useful service for professionals such as attorneys to bill clients for long distance phone calls made on their behalf. A problem with this subaccount billing service is that the customer must presubscribe to the service and pay a periodic charge for the service regardless of how many subaccount billing calls, if any, are made.